Without Claymore and ZEC I probably should throw away or sell cheap my 50+ R9 280X cards.. so - respect. 
If your planning on binning them I'll happily take them off your hands for free
I will let You know if I am ready to bin cards.
Until ZEC is still profitable for 280Xs it will not happen.
I think Zec has reached its level now, at about the $50-$55 area. I cant really see it dropping to much in price now.
Main thing I can see affecting profitability going forwards I think will be the difficulty.
Agreed, if it gets any lower than $50 I'll be going back to ETH or Monero